Impacts of Critical Periods of Weed Control (CPWC) on Nitrogen Utilization and Grain Yield in Aerobic Rice Cultivation

Abstract

The cultivation of aerobic rice appears to be a potential option while mitigating threats of looming water scarcity for sustainable rice production. Although, severe prevalence of multi-flush weed pressure inhibiting nitrogen utilization for optimum grain yield becomes the crux of the problem for up-scaling this technology. Thus, the hypothesis of the study was that critical period of weed control (CPWC) governs nitrogen accumulation in aerobic soil—plant continuum, which appears to be the major determinant of ultimate grain yield in aerobic rice cultivation. With this view, the field studies were successively conducted in two locations at Panthnagar, Uttar Pradesh during 2015 and at Cuttack, Odisha during 2016 in India. Nitrogen utilization was estimated with varying magnitude of critical period of weed prevalence at 15 days interval since sowing till 75 days of crop growth. Results recorded significantly higher nitrogen uptakes of 106.6 and 106.0 kg ha⁻¹ while maintaining near weed-free situations during initial 75 days of crop growth at Panthnagar and Cuttack respectively, which were however comparable with similar situations maintained also at 60 and 45 days of crop growth in respective location. Consequently, stands at these situations produced comparable grain yield of 5.56 and 5.25 t ha⁻¹, 5.40 and 5.00 t ha⁻¹, and 5.15 and 4.70 t ha⁻¹ at corresponding locations, which were significantly higher than those corresponding weedy stands producing 1.35 and 0.90 t ha⁻¹, 1.48 and 1.10 t ha⁻¹, and 2.86 and 2.45 t ha⁻¹ grain yields in respective locations. Thus, higher nitrogen gains of 0.42 and 0.06%, and 0.31 and 0.03% were attributed to initial 75 and 60 days weed-free stands respectively at Panthnagar and Cuttack. While, nitrogen losses were maximum of 24.99 and 25.69%, and 24.26 and 24.85% at corresponding weedy crop stands; although, initial 15 day’s weedy crop stands or initial 45 days weed-free stands recorded the lowest nitrogen losses of 0.64 and 1.35%, and 1.51 and 2.16%, instead. Therefore, the study contributed above novel information explaining the dynamic correlation of nitrogen balance with prevalence and also magnitude of CPWC where N uptake culminated at 45 days weed-free situation ensuring optimum aerobic rice productivity.